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Diisocyanates - Health Surveillance and Monitoring

Health Surveillance

Health surveillance is putting in place systematic, regular and appropriate procedures to detect early signs of work related ill health and then acting upon the results. Further information on how to set up a Health Surveillance program can be found at this LINK.

  • Employer - Make respiratory health surveillance programme available for all relevant employees, e.g. lung function testing.
  • Employer - Make a skin health surveillance programme available for dermatitis (skin checks for dryness/soreness).
  • Employee - It is important to seek medical advice if there are persistent symptoms and report these to the employer.

There is evidence that both respiratory and dermal exposures can lead to sensitization . A good Health Surveillance Program will allow for the early recognition of sensitization. Prompt and strict elimination of exposures is essential to reduce the risk of long-term or permanent respiratory problems for workers who have become sensitized.

Biological Monitoring can also be part of your health surveillance program.


Air Monitoring

In relation to air monitoring, there are several issues with current methods for air sampling of isocyanates. Taking only one or two personal samples for air monitoring, limits our ability to understand a worker’s real exposure and is not statistically significant. For example a preliminary test in EN689 requires that where three measurements are taken, all results should be <10% OEL. As inhalation is only 1 route of exposure, a low air monitoring result is not sufficient on its own to complete the risk assessment and determine controls. Several isocyanate compounds are absorbed across the skin. All routes of exposure must be considered.

The UK Methods of Determination of Hazardous Substances (MDHS 25/4 )can be used for the determination of time-weighted average concentrations of organic isocyanates in workplace atmospheres. The method requires the use of a glass impinger containing 1-(2-methoxyphenyl)piperazine (1,2-MP) absorbing solution backed with a filter impregnated with 1,2-MP reagent (isocyanate aerosols) or alternatively a single filter impregnated with the 1,2-MP reagent (isocyanate vapour).
“1-(2-methoxyphenyl)piperazine” is classed as a controlled substance in Ireland under Schedule 1, of the Misuse of Drugs Regulations. Please be advised that any establishment that intends to possess this controlled substance on site would require a controlled drug annual licence, issued by the HPRA on behalf of the Department of Health, in order to do so. In addition, any establishment that intends to import/export this controlled substance into/out of Ireland would require a controlled drug import and/or export licence, per consignment, in order to import/export this controlled substance. See www.hpra.ie.

There are similar restrictions in the United Kingdom. The British Occupational Hygiene Society Group Authority license only applies to members of the Faculty of Occupational Hygiene and does not apply to use in the Republic of Ireland.

Alternative sampling methods are available for isocyanates, however, they have drawbacks.

  • They typically fail to measure the total reactive isocyanate group (TRIG) concentration necessary for direct comparison with the OEL.
  • It is important that any method captures both the aerosol and vapour phases.
  • In addition, there is evidence that dermal exposures can lead to sensitization. Air monitoring will not measure this exposure so the risk will be underestimated.
  • Surface monitoring techniques can change colour in presence of some isocyanates – this only indicates presence, not amount.

There is research underway to develop alternative methods for air monitoring.

Based on all of these, air sampling for isocyanates is unlikely to provide reliable, usable valuable data. An alternative is to use biological monitoring. See Biological Monitoring Guidelines